In the UK I am trying to stick to E5 ( 99 octane 5% ethanol) for everything. Even handbooks for vehicles less than 1 year old seem to grudgingly say that E10 can be used but E5 is preferred. Its not so much about performance but more about the as yet unknown long term effects that may or may not cause deterioration of non-metallic parts of the fuel system. Time will tell! My vehicles in everyday use achieve 50, 75+, and 150+ miles per UK gallon respectively, so the premium price doesn't hit my pocket too hard.